ᐅ The trap is draining too slowly, fitting for an older on-demand water heater

Hello everyone,

During my bathroom renovation, two issues have come up:

1. I installed a designer siphon with angles that are almost perfectly right-angled (if that is relevant). However, the water is not draining properly. The pipe leading upward fills up quickly, and the water either comes back up through the drain fitting or remains standing in the basin.

Does anyone have an explanation for this or a common beginner’s mistake?

2. We have a relatively old tankless water heater directly connected to the faucet, as shown in the pictures. The water flow and temperature are controlled by two separate handles. Is there a way to install a surface-mounted faucet connected to the tankless water heater by a hose, which would allow controlling both hot and cold water from the faucet itself? In other words, without using the two-handle control.

Thanks in advance and best regards,

Peter